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From:   Valentin Schneider <vschneid@redhat.com>
To:     Leonardo Bras <leobras@redhat.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Leonardo Bras <leobras@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Juergen Gross <jgross@suse.com>,
        Yury Norov <yury.norov@gmail.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v5 1/2] trace,smp: Add tracepoints around remotelly
 called functions
In-Reply-To: <20230615065944.188876-5-leobras@redhat.com>
References: <20230615065944.188876-3-leobras@redhat.com>
 <20230615065944.188876-5-leobras@redhat.com>
Date:   Thu, 15 Jun 2023 17:42:36 +0100
Message-ID: <xhsmh5y7oy8w3.mognet@vschneid.remote.csb>
MIME-Version: 1.0
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On 15/06/23 03:59, Leonardo Bras wrote:
> The recently added ipi_send_{cpu,cpumask} tracepoints allow finding sources
> of IPIs targeting CPUs running latency-sensitive applications.
>
> For NOHZ_FULL CPUs, all IPIs are interference, and those tracepoints are
> sufficient to find them and work on getting rid of them. In some setups
> however, not *all* IPIs are to be suppressed, but long-running IPI
> callbacks can still be problematic.
>
> Add a pair of tracepoints to mark the start and end of processing a CSD IPI
> callback, similar to what exists for softirq, workqueue or timer callbacks.
>
> Signed-off-by: Leonardo Bras <leobras@redhat.com>

Tested-and-reviewed-by: Valentin Schneider <vschneid@redhat.com>